After being used in a reactor, irradiated fuel elements are deactivated and then transported to reprocessing installations where they are stored and then subjected to various processes in order to extract the radioactive materials which are then confined and stored in accordance with the applicable safety regulations in order to protect the population and the environment.
Regardless of the type of reactor concerned, (Pressurized Water Reactor PWR, Boiling Water Reactor BWR, etc.) each fuel element comprises two metal parts referred to as "end pieces" and a plurality of fuel rods held therebetween.
For example, in a PWR, there are several hundred fuel rods each of which is constituted by a fuel-containing metal tube which is several meters long and 1 cm to 1.5 cm in diameter, with said tubes being held mutually parallel by transverse metal spacers and having their ends engaged in respective end pieces, and with the cross-section of an entire fuel element being, for example, a square having a side of about 30 cm.
The first reprocessing stage consists in cutting up the fuel element in a shearing cell, with the end pieces being cut off and the rods being cut up. The resulting cut-up rods are sent to a dissolver in which hot nitric acid dissolves the fuel while leaving the metal parts intact.
In order to avoid damage to the dissolver, and in order to avoid clogging it up pointlessly, the end pieces are removed separately from the rods and taken to a specific processing location (for washing, compacting, encasing, etc.).
A first way of doing this consists in cutting off the end pieces and cutting up the rods in different locations. Thus, French patent number 1,587,331 describes the two end pieces being sawn off at a sawing station with the fuel element then being displaced on swing-trays to bring them to the rod cutting-up station. In this way, the end pieces and the rods are removed separately.
In order to avoid the need to displace the fuel element without its end pieces, which requires special precautions to be taken in order to hold the rods together, French patent number 75-27 897 describes a method and an associated apparatus applicable to intact fuel elements (whose end pieces have not been previously removed therefrom), in which method the first end piece (the one closest to the cutting section) is separated from the rods, the rods are then cut up, and the last end piece is then removed, with the same blade being used for cutting off the end pieces and cutting up the rods and with the same opening being used for their removal .